packages,plugins: add package documentation

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/badges-backend/api-report.md

@@ -139,6 +139,4 @@ export interface RouterOptions {
   // (undocumented)
   discovery: PluginEndpointDiscovery;
 }
-
-// (No @packageDocumentation comment for this package)
 ```

plugins/badges-backend/src/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+/**
+ * A Backstage backend plugin that generates README badges for your entities
+ *
+ * @packageDocumentation
+ */
+
 export * from './badges';
 export * from './lib';
 export * from './service/router';